Over time and through repeated use, bones and joints can become damaged or worn. For example, repetitive strain on bones and joints (e.g., through athletic activity), traumatic events, and certain diseases (e.g., arthritis) can cause cartilage in joint areas, for example, which normally provides a cushioning effect, to wear down. When the cartilage wears down, fluid can accumulate in the joint areas, resulting in pain, stiffness, and decreased mobility. The same can happen in cases where tendons in a joint become lax or soft tissues in or adjacent the joint tear becomes damaged or worn.
Arthroplasty procedures can be used to repair such damaged joints. During a typical arthroplasty procedure, an arthritic or otherwise dysfunctional joint can be remodeled or realigned. A prosthesis or prostheses can be implanted to repair the damaged region. Arthroplasty procedures may take place in any of a number of different regions of the body, such as the knees, hips, shoulders, or elbows, for example.
One type of arthroplasty procedure is a shoulder arthroplasty, in which a damaged shoulder joint may be replaced with prosthetic implants. The shoulder joint may have been damaged by, for example, arthritis (e.g., severe osteoarthritis or degenerative arthritis), trauma, or a rare destructive joint disease.
Prostheses that are implanted into a damaged region may provide support and structure to the damaged region, and may help to restore the damaged region, thereby enhancing its functionality. Prior to implantation of a prosthesis in a damaged region, the damaged region may be prepared to receive the prosthesis. In the case of a shoulder arthroplasty procedure, one or more of the bones in the shoulder area, such as the humerus and/or glenoid, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) to provide one or more surfaces that can align with the implant and thereby accommodate the implant. Standard alignment instrumentation and/or patient-specific guides may be used for locating a position and orientation to resect the humeral head for proper humeral stem placement.
Accuracy in implant alignment is an important factor to the success of a surgical procedure. A one to two millimeter translational misalignment, or a one to two degree rotational misalignment, may result in imbalanced ligaments, and may thereby significantly affect the outcome of the procedure. For example, implant misalignment may result in intolerable post-surgery pain, and also may prevent the patient from having proper deltoid tension or range of motion.
To achieve accurate implant alignment, prior to treating (e.g., cutting, drilling, reaming, and/or resurfacing) any regions of a bone, it is important to correctly determine the location at which the treatment will take place and how the treatment will be oriented. It is also often preferable to maintain as much of a patient's natural bone stock as possible during such a procedure. Prostheses generally have a certain life expectancy and in certain cases need to be replaced at some point. If one or more prostheses need to be removed and/or replaced in a revision procedure, a large bone void could be left after their removal. In certain cases, this bone void is not ideal for receipt of revision components. While bone cement can be added to the void to fill space and/or secure revision components, it is generally not a preferred option. Preserving natural bone stock may be vital for the ability to even perform a revision procedure. There exists a need for maintaining the stability and/or positioning of primary components in a revision procedure.